The present application claims priority under 35 U.S.C. 119 of German Patent Application No. DE 200 19 109.8 filed Nov. 12, 2000.
The complete disclosures of the following three copending, commonly-owned U.S. patent applications filed concurrently with the present application are hereby incorporated by reference into the present specification: U.S. patent application Ser. No. 10/008285 (Attorney Reference LAGP:109_US_; corresponds to German Application No. 200 19 106.3 filed Nov. 12, 2000); U.S. patent application Ser. No. 10/007168 (Attorney Reference LAGP:110_US_, corresponds to German Application No. 200 19 107.1 filed Nov. 12, 2000); and U.S. patent application Ser. No. 10/010101 (Attorney Reference LAGP:111_US_; corresponds to German Application No. DE 200 19 105.5 filed Nov. 12, 2000).
The invention relates to a stand, more particularly to a stand for a surgical microscope which compensates for the weight of the microscope and any additional devices.
It must be easy for surgical microscopes to be able to pivot over a wide, prescribed range. In addition, once a surgical microscope is properly positioned, the microscope stand should be capable of easily holding a microscope in the desired position. For this reason, microscope stands are provided with balance weights which compensate for the weight of the microscope and any additional devices. The balance weights are frequently arranged in the manner of beam-type balances. Particular embodiments of such beam-type balance arrangements are, for example, the xe2x80x9cOHS(trademark)xe2x80x9d design, in which balance weights are displaced from top to bottom via parallelogram carriers such that the overall centroid of the stand is situated in the lower region of the stand structure. The design principle of the OHS(trademark) is illustrated symbolically in the International Patent Application WO 97/13997.
A further design, xe2x80x9cMS 1xe2x80x9d provides a balance device for ease of operability of the microscope and movability of the latter in space. This balance device also provides for the relevant compensation of changes in the weight of the microscope; adding or removing additional devices on the microscope is conducted via a pressure spring, which is clamped obliquely or diagonally in a parallelogram carrier. This parallelogram carrier serves as a pivotable horizontal carrier for the microscope. In the International Patent Application No. WO 99/1693 (Bees), the design of the MS 1 is illustrated symbolically and the particular parallelogram carrier design has been published in European Patent Application No. EP 433426 A1 (WO 91/472).
For the purpose of improved tilt stability, MS 1 provides a switchbox which contains the electric power supply for the microscope, its illuminating device, its controllers or the like and, if appropriate, any additional weight. The switchbox is mounted rigidly on the vertical support column of the stand and undertakes there only balancing over the vertical axis of the upright support column with regard to improving the tilting moment of the stand.
DE 19742050 A1 refers to an article xe2x80x9cGewichtsausgleich an feinmechanischen Gerxc3xa4tenxe2x80x9d [xe2x80x9cBalancing on fine-mechanical equipmentxe2x80x9d], which was published by Hilpert in No. 2/1965 of the journal Feingerxc3xa4tetechnik, Volume 14. In this article from 1965, there is a detailed discussion of various weight-compensating measures in fine mechanics, which are achieved principally not by a counterweight, but by spring-compensating measures (such as, by way of comparison, only in the case of the MS 1 design).
DD 221571 A1 (1985) describes a stand design having a lever arm, which is weight-compensated by the spring which is connected to the lever arm via a cable pull. The surgical microscope is located at the distal end of the lever arm. The fundamental adjustment of this surgical microscope is performed via a threaded spindle which is used to draw the end of the spring fixed to the housing further from the lever arm, or to guide it nearer to it. Changes in weight at the microscope are compensated by the fact that the pivoting point of the cable pull is adjusted relative to the lever arm via a spindle. In order to achieve a uniform countermoment in all possible angular positions, it is necessary for the abovementioned point of action of the cable pull to be located on a connecting line between the axis of rotation of the lever arm and the centroid of the microscope. This is achieved by actuating an adjusting device in the form of a worm gear, which rotates a disc, connected to the lever arm, about the axis of rotation of the lever arm. This design requires a great number of adjusting measures in order to achieve the desired effect. In this case, the disc-worm design prevents, independently of the weight, the possibility of selecting any desired position of the microscope. Apart from this, the construction of this known design necessitates a high overall centroid of the stand, since all the balancing devices are arranged above the microscope.
DE 3739080 A1 (1989), likewise, specifies a spring device for balancing stands where cable pulls combined with springs are intended to lead to balancing. However, this publication discloses forcing support and adjustable movement which is exercised by an operator on a handle. This patent does not teach holding a load in a counterbalanced xe2x80x9cfloating statexe2x80x9d as is desired when using a surgical microscope.
By contrast, U.S. Pat. No. 5,397,323 (1992) presents a surgical robot having parallelogram carriers, in the case of which, inter alia, the weight of the instrument is held in a weight-compensated fashion via a cable pull with the aid of a counterweight. The cable pull is of closed design in this case, that is to say that one cable in each case is guided from the instrument up to the counterweight over an upper and lower deflecting roller (FIG. 3 of U.S. Pat. No. 5,397,323). Such a design presupposes that the counterweight is attached in the immediate vicinity of the instrument. It could therefore be applied only poorly for use on a surgical microscope. Its technical teaching is therefore not obvious for adaptation to a stand for microscopes.
Stands without a pivoting arm but with balancing by means of tape pulls over a single deflecting roller directly on the support column were marketed under the designation xe2x80x9cStandardxe2x80x9d and xe2x80x9cUniversalxe2x80x9d. However, these had no pivoting arm, and the balancing is limited to equalizing the vertical load of the support arm directly on the support column. The tapes which transmitted the force run exclusively parallel to and immediately next to the support column. They act not on the support arm, but on a ring directly on the support column, which held the laterally projecting support arm. In the event of a change in load, it is necessary to change the balance weight if proper balance is desired.
DE 19742050 A1 (1999) discloses a stand design having a pivotable parallelogram carrier which is weight-compensated via a cable pull and a balancing spring such that the additionally present balance weights, which act in accordance with the abovementioned principle of the balance, can be designed to be particularly small. In this design, the cable pull is guided in a special way in order to minimize the balancing error, caused by the finite deflecting radius, in a wide pivoting range. The balancing error is, however, not eliminated by this measure, and so in specific pivoting positions it remains necessary to adjust the balance weights.
U.S. Pat. No. 6,070,839 (2000) discloses a further design having a pivoting arm and a cable pull-spring structure which permits pure balancing (in the sense of the abovementioned balancing with a diagonal bearing spring) but also without contributing balancing moments to an improvement in the tilt stability. In the case of changes in weight, the pivoting point of the cable pull is displaced, in a fashion comparable to the design in the abovementioned DD 221571, over a spindle.
U.S. Pat. No. 5,253,832 (1999) describes a stand having a centrally arranged tension spring for the balancing. This design offers no simple adjustability for changed loads, and so changes to a microscope or to its accessory equipment cannot lead directly to an adjustment of the equilibrants. In addition, it is disadvantageous that, as a function of the pivoting position of the support arm, the tension spring has a different degree of compression or expansion and, owing to the spring characteristic; this leads to different equilibrants and, thus, to a balancing response which differs over the pivoting range of the support arm and is therefore ineffective to a user in the surgical field.
By contrast with these known designs, the object of the present invention is to create a novel stand, in particular, a stand for surgical microscopes, which, independently of the (pivoting) position of the microscope, effects an optimum possibility of compensation for changes to the load (surgical microscope) with the lowest possible outlay on adjustment.
This object is achieved by using a novel counterbalancing transmission which compensates a changed weight condition at the load (surgical microscope) by virtue of the fact that a constantly acting equilibrant (spring, weight or the like) affects the support arm of the load at a different transmission ratio, doing so independently of the position (pivoting position) of the load.
Various embodiments and developments of these embodiments occur within the scope of this fundamental idea of the invention as they are specified in the dependent claims and become evident to the person skilled in the art on the basis of the data, and if appropriate, taking account of the teachings of the patent applications of the same date mentioned below.
Springs are ideal for particularly powerful weight compensation in a small space. Both tension springs and pressure springs are suitable, depending on the attachment site. Springs which apply the same force over a specific compression or expansion path would be ideal in theory. However, such springs cannot be used in a comparable design having the comparable parameters. Consequently, use is preferably made of conventional springs which, however, tolerate a movement (pivoting high and low) of the load by means of compensation equalizing in the form of cams or the like, in order always to apply the same compensation force or compensation moments.
A design such that the device for generating a constant force is not a spring but a balance weight guided on a cable pull has proved to be another advantageous variant. Reference is made in this connection to U.S. patent application Ser. No. 10/010101 (Attorney Ref. LAGP:111_US_; corresponds to German Application No. DE 200 19 105.5 filed Nov. 12, 2000) which was filed on the same date and considers the particularities and further ideas of the invention, independent from the one above, in conjunction with balancing measures on a stand which are supported by cables and weights. If a design corresponding to U.S. patent application Ser. No. 10/010101 (Attorney Ref. LAGP:111_US_; corresponds to German Application No. DE 200 19 105.5 filed Nov. 12, 2000) is selected, in addition to the weight-compensating effects, this also produces compensatory measures for improving the tilt stability of the stand.
Within the scope of the present application and without combination with the teaching of U.S. patent application Ser. No. 10/010101 (Attorney Ref. LAGP:111_US_; corresponds to German Application No. DE 200 19 105.5 filed Nov. 12, 2000), effects independent of tilting moment also occur in the case of a particular configuration of the counterbalancing transmission when the counterbalancing transmission is designed such that at least a portion of its mechanics is provided on the side of the vertical carrier diverted from the load, and that at least a portion of the device supplying the constant force is situated on the same side.
In addition to the abovementioned patent application U.S. patent application Ser. No. 10/010101 (Attorney Ref. LAGP:111_US_; corresponds to German Application No. DE 200 19 105.5 filed Nov. 12, 2000), the applications U.S. patent application Ser. No. 10/007168 (Attorney Reference LAGP:110_US_; corresponds to German Application No. 200 19 107.1 filed Nov. 12, 2000) and U.S. patent application Ser. No. 10/008285 (Attorney Reference LAGP:109_US_; corresponds to German Application No. 200 19 106.3 filed Nov. 12, 2000) were also filed on the same date, all of these likewise referring to a stand design which, in a preferred embodiment, combines the combinations of features from these patent applications which are independent according to the invention.
With regard to their disclosure, the present and the abovementioned patent applications form a single entity, and the aim is for it to be possible to combine the elements illustrated in one and the other application with regard to subsequent applications in the sense of a completely novel stand concept in which the two inventions are united.